The present invention relates to the catalytic gas phase oxidation of toluene with a gas containing molecular oxygen in the presence of a silver vanadate catalyst which conversion yields benzaldehyde, benzoic acid or both products.
A process for the catalytic oxidation of toluene with molecular oxygen, including ozone, is described in British Patent Specification 1,164,316, which is hereby incorporated by reference. According to this reference catalysts based on silver vanadate show, in addition to a reasonable degree of activity, a particularly good selectivity, that is only a small portion of the oxidized amount of toluene changes over into valueless carbon dioxide, while the remainder consists principally of the desired benzaldehyde and benzoic acid products.
It is also known to catalytically oxidize toluene in the vapor phase with oxygen or ozone to benzaldehyde using as the catalyst a mixture of silver vanadate with lead vanadate or silver arsenate. This catalyst system suppresses both the formation of benzoic acid and degradation to carbon dioxide and is described in commonly assigned U.S. Pat. No. 3,485,876, the disclosure of which is hereby incorporated by reference. As explained in this patent selectivity of the catalyst determines the quality of the product, such as the percentage of the desired product. The activity of a catalyst determines the rate of conversion, that is the percentage of starting material converted into the product.